Hadith 3795
´It was narrated that Ibn 'Umar said:` "The Messenger of Allah said: 'Whoever swears, let him not swear by anything other than Allah.'" The Quraish used to swear by their forefathers, and so he said: "Do not swear by your forefathers."
Hadith 3796
´Yahya bin Abi Ishaq said:` "A man from Banu Ghifar told me, in the gathering of Salim bin 'Abdullah, Salim bin 'Abdullah said: 'I heard 'Abdullah -that is, Ibn 'Umar- say: "The Messenger of Allah said: 'Allah forbids you to swear by your forefathers.'"'"